The purpose of the research project is to study antigen sharing between Schistosoma mansoni cercaria and adults and their intermediate host, Biomphalaria pfeifferi. Progress to date has included the localization of mimicked snail antigens on adult worms by means of peroxidase labeled antibody, and the partial purification of this antigen from freeze thaw or homogenate preparations of whole worms. Some preliminary chemical characterization studies indicate that the mimicked antigen is heat labile, TCA precipitable, non-dialyzable, and present in the first peak from a Sephadex G-200 column. The antigen does not bind to Cibacron Blue Sephadex and stains as a protein but not as a lipid or carbohydrate. Isolation of the antigen from snail homogenate preparations has been hampered by the non-specific binding of several snail components to mouse and rabbit serum.